This application claims the priority of German patent document 196 51 671.4, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a control of an injection system for a multicylinder internal combustion engine, especially for a Diesel engine.
A control and a fuel injection system of this generic type are described in German patent document DE 43 35 171 C1. This known fuel injection system makes it possible to detect leaks in the system and to close off a line that is leaking. The known system however is only effective for larger leaks.
The object of the present invention is to provide an improved fuel injection control arrangement, which has increased accuracy.
Another object of the invention is to provide a control which can detect even smaller leaks so that appropriate measures can be taken in such cases.
These and other objects and advantages are achieved by the fuel injection control according to the invention, which is premised on the proposition that the control electronics of an engine basically detects small leaks in the system, but it is not clear exactly where the leaks are located and how extensive they are. According to the invention, the line in which a major leak occurs is shut off by the piston which is upstream of the leaking line in its throttle position, due to the pressure drop behind the piston and the delivery of fuel in a throttled state. The piston, therefore, automatically blocks the associated branch line.
Smaller leaks that do not produce an immediate large pressure drop (to which the associated piston and its throttle point would react) are also detected by the control system according to the invention and their locations pinpointed. If the system detects even a small pressure drop in the system, the injection valves of a branch line are simply shut off or kept closed as a precaution while fuel continues to be delivered via the other branch line. If the system finally determines that there is no longer a leak, this means that the correct branch line was "accidentally" shut off. The branch line in which there is no leak can then continue in emergency operation, with a reduced volume of fuel being delivered.
If, however, the system determines that the leak is still present after the injection valves of a branch line are shut off, the shut-off injection valves are activated once again during a delivery pause of the high-pressure pump. As a result of the reduced pressure thus produced in the branch line, the associated sealing piston then automatically shuts off the leaking line. The other branch line can then continue emergency operation, with a reduced volume being injected.
The control according to the invention makes it possible to detect all kinds of leaks in this fashion, and can adopt appropriate countermeasures independently. In order to increase the sensitivity of the response, according to an embodiment of the invention, when smaller leaks develop, the check is initiated by fuel injection with an excess volume, with simultaneous reduction of the volume delivered.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.